I have no knowledge about how the mautic plugin is supposed to work by own experience. But I guess you first need to set up a mautic installation on your server (mautic to be taken from http://www.mautic.org/ - which seems to be down or https://github.com/mautic/mautic). When the mautic installation is runner on your server you would have to provide the Elgg mautic plugin with the url of this installation in the mautic plugin settings. And most likely you can view the tracked data then on the mautic installation.